The concept of interlocking toy building blocks with interconnecting, releasable hinges was first introduced in the prior art in U.S. Pat. No. 4,606,732, issued Aug. 19, 1986 to Ronald Lyman. In addition to interconnection means for stacking such blocks in rigid assembly, this patent discloses the provision of hinge arms extending from one end of each block, and recessed portions at the other end of each block to snap-engage the hinge arms of a similarly formed block. These features expand the structural potential for such building block systems by providing end connections in addition to the vertical stacking capability, and, in particular, by providing pivoting end connections between end-adjacent blocks. Thus it becomes possible to form representations of curved surfaces, to form moving structures which pivot and rotate and, in general, to greatly increase the possibilities for artistic and recreational expression through the medium of building block construction.